The present invention relates to a fiber optic laser conducting and diffusion device used for a laser dynamic therapy for an early cancer, the laser dynamic therapy known as a photodynamic therapy.
The laser dynamic therapy for an early cancer is performed, while observing the body cavity by an endoscope, irradiating a laser beam in the amount as necessary against the affected part by a fiber optic laser conducting and diffusion device inserted through a forceps aperture of the endoscope. Particularly, it is necessary to provide at the extreme end of the device a tip capable of carrying out the irradiation of a laser beam in response to shapes of the body cavity such as tubular organs such as a throat and a cervical canal, and bag-like organs such as a stomach and kidney. For that purpose, methods heretofore proposed include U.S. Pat. Nos. 4,693,556 and 4,660,925 in which a tip is formed at the extreme end by an ultraviolet hardening resin containing a fine powder of quartz to provide a uniform diffusion of light; U.S. Pat. No. 4,676,231 in which a transparent liquid with fine particles suspended is put into a hollow transparent tip; and U.S. Pat. No. 4,646,151 which suggests in its specification and drawings that an epoxy resin mixed with light diffusion particles is coated on an internal surface of a hollow transparent tip.
In case a pulse wave laser beam is used, an end tip formed of an inorganic material (Examples: quartz, sapphire, glass, etc.) tends to be easily cracked and broken, which is dangerous, when the concentration and high densification of shock waves generated from a pulse laser occur. A similar situation tends to occur in a tip which uses hard plastics (Examples: polymethylmethacrylate resin, polystyrene resin, etc.). Among the plastics, materials having a polar group within molecules which have a tendency of molecular polarization (Examples: polytetrafluoroethylene resin, polyamide resin, polycarbonate resin, epoxy resin, etc.) cause the inner surface of the tip to be blackened to deteriorate the light irradiating performance.
On the other hand, a tip made of polyacetal resin known as Derlin (a trademark of Du Pont) has a possibility to generate formalin which is injurious to the living body due to the thermal decomposition by laser.
As described above, it is necessary to select very carefully a tip for diffusion of a pulse laser beam different from a continuous wave laser.